Bill Shorten has apologised for mistakenly telling Parliament that Liberal frontbencher Michael Ronaldson called the former Chief of Army Ken Gillespie a ''coward''.

The Opposition Leader apologised on Wednesday night, after receiving a letter from Senator Ronaldson demanding to see the evidence for his ''coward'' claim. It also came after a day spent trying to deflect attention from comments made by Labor frontbench colleague Stephen Conroy.

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Trying to deflect attention from Senator Conroy's attack on General Campbell, Mr Shorten told the House on Wednesday: ''What I also know is that . . . when Chief of Army General Gillespie was at estimates it was Senator Ronaldson who called him a coward,'' during debate on a motion to admonish Senator Conroy.

But the Special Minister of State, Senator Ronaldson, had no recollection of calling General Gillespie a ''coward'' at an estimates hearing in 2011. And when he phoned the General to check, the former Chief of Army also did not recall the exchange.

Senator Ronaldson wrote to Mr Shorten's office asking to see evidence for his claim.

Opposition Leader Bill Shorten has had to apologise to Parliament over comments made mistakenly in defence of Senator Stephen Conroy. Photo: Alex Ellinghausen

''I wrote to Mr Shorten asking him to provide me with a copy of the transcript showing me where I allegedly said this,'' Senator Ronaldson said.

Mr Shorten's staff could find nothing in the parliamentary record to support his ''coward'' claim.

It is understood Mr Shorten received the letter from Senator Ronaldson at 7.20pm and at 7.26pm he entered the House to correct the record and apologise.

''This afternoon I referred to the Special Minister of State,'' Mr Shorten said. ''At the time I had been advised that the minister had made the remark I attributed to him.

''Tonight at 7.20pm, I received a letter from the Special Minister of State advising that he has no recollection of making that remark.

''Therefore, I wish to correct the record and I apologise to the Special Minister of State.''

Mr Shorten got the ''coward'' tip from his Victorian Labor colleague David Feeney. Mr Feeney had passed a note to the Opposition Leader telling him about Senator Ronaldson's alleged exchange with the Chief of Army in 2011.

When Fairfax Media called Mr Feeney on Thursday morning, the member for Batman admitted he might have unwittingly misinformed his leader.

''I witnessed a couple of sharp altercations [between Senator Ronaldson and General Gillespie],'' Mr Feeney said, though acknowledging there was a difference between a "sharp altercation'' and calling the Chief of Army a ''coward''.

''But the critical point here is that this is a device for the Liberal Party to avoid talking about issues that actually matter,'' Mr Feeney said, citing ''secrecy, Manus Island, cuts to Defence and the difficulties that Senator Nash is experiencing''.

Senator Ronaldson said he wanted a ''formal retraction'' from the Opposition Leader.

''The only way the record can be properly corrected is for a full and unequivocal retraction of the allegation and this must be done in the House by Mr Shorten,'' he said.

''Notwithstanding the rough and tumble of Parliamentary proceedings, Mr Shorten's accusation went way beyond acceptable standards.''

Independent MP Andrew Wilkie, who initiated a parliamentary censure of Senator Conroy believes he can remain opposition defence spokesman provided he apologises to General Campbell.

Mr Wilkie said it was entirely appropriate to quiz General Campbell about Operation Sovereign Borders.

''But what happened was, Senator Conroy accused General Campbell of being complicit in a cover-up when there is no evidence,'' he told ABC radio on Thursday.

''It was a direct attack on his character and it was entirely unwarranted,'' he said.

Mr Wilkie said Senator Conroy should face the media and publicly apologise to General Campbell.

''Say he made a mistake, that he’ll learn from it and he’ll get back to work,'' he said.